Railway car wheel maintenance poses several challenges. What is commonly called a "wheel" is in fact more accurately defined as a wheel assembly, which includes an axle with two flanged wheels press fit thereon. When an axle cracks or bends, the flanged wheels are damaged or require refinishing, a standard maintenance procedure is performed to remove the damaged wheel assembly and install a replacement.
Rail cars with damaged wheels may of course require maintenance anywhere along a railroad track. In some cases moving the rail car could be dangerous or inconvenient. In all cases the speed of the wheel change operation is important since a stationary rail car generates little revenue, and the damaged car may be blocking rail traffic. The location of the damaged rail car may be remote from repair facilities. The terrain adjacent the railway tracks is often very rough and access restricted.
Conventional responses to this problem have been partially successful. If the damaged car can be easily moved to a repair shed, a common solution is to lift the rail car with an overhead crane and then to replace the wheel. Often the time, cost and inconvenience involved in uncoupling the damaged car from a train, moving the car to a repair shed, and rerouting the freight, make this type of operation very unsatisfactory.
A preferred repair operation involves quickly replacing the damaged wheels of rail car while it rests on the rails without moving the rail car substantially. In emergency situations, rough terrain mobile cranes have been used to lift rail cars and perform repairs. Mobile cranes are expensive to operate and require large areas on or adjacent the tracks. The mobile crane must be transported to the site, and may require substantial labour and equipment to properly set up. It is unsafe to work close to or under a heavy load suspended by a crane and therefore safety concerns require that the rail car be securely positioned on blocks before workers can commence repairs.
Several systems have been introduced which use hydraulic jacks to lift the rail cars while they rest upon the rail tracks. Hydraulic jacks are relatively easy to transport and insert under rail cars. As well hydraulic jacks provide a stable base on which the car can rest during repairs.
Hydraulic jacks may be placed under the trucks of the rail car to lift the trucks off the damaged wheel. The jacks must be supported on blocks and levelled however increasing the repair time taken. A preferred method is to use the relatively level rail tracks for supporting jacks to lift the rail car. An example of one such system is described in U.S. Pat. No. 4,068,823 to Belanger.
Due to the limited space available under the rail car trucks, the lifting capacity and maximum lift of such jacks is severely limited. In short, the more space that is available, the larger the jack, and the higher and heavier the capacity of the jack. To replace a rail car wheel, the lifting height capacity of such systems is simply inadequate.
Boxcars and container rail cars have structural frames with longitudinal beams. These beams of the frame have sufficient strength that enable the rail car can be safely lifted by placing hydraulic jacks on the rail tracks for support and extending the jacks upward to lift under the beams.
Prior art devices include systems where hydraulic jacks are supported on the rails in the midportion of the rail car. The jack is extended upwards to engage the underside of the rail car beam or frame to lift the rail car. Examples of such systems are described in U.S. Pat. Nos. 4,805,875 to Jackson et al and 5,133,531 to Grashoff et al. There is ample space in the midportion of the car to utilize high lift capacity jacks, or as in the case of Grashoff, to position hydraulics outboard of the car.
A significant advantage of lifting in the midportion is realized when the jacks are used on articulated well cars. Whereas conventional cars have two trucks, one at either end of a rail car, well car trains are assembled from car platforms which share a common articulated track between them. The jack may be positioned in the midportion of one car to lift the car, an adjacent portion of the next car and shared truck off a damaged wheel. As such the jack is distant from the wheel and there is sufficient access space to replace the wheel.
Although well cars are used extensively for transporting containers and other specialty large height loads, they still represent only a fraction of the modem rail car traffic.
The obvious disadvantage of using a midsection lifting system is that it cannot be used on rail cars that do not have accessible structural frames or beams. Tanker rail cars are constructed as cylindrical tanks supported at their ends on trucks which are coupled together. Grain cars or ore cars often have hoppers, conveyor pipes, trapdoors and other hardware extending below the midportion of the car. Jacking in this area is either impossible due to insufficient structural strength, or is likely to damage such hardware. The acceptance of such midportion hydraulic lifting systems is severely limited since trains are generally assembled with an unpredictable variety of rail cars and a system that cannot be used on all cars of a train is less than ideal.
It is desirable therefore to produce a hydraulic lifting system that can be utilized regardless of the type of rail car or the nature of its structural frame. Ideally such a desired system would be easily transported and handled during the setup procedure.
It is also desirable to produce a lifting system which is simple to set up and does not require separation of the rail cars from an assembled train.